1. Field of the Invention
This invention relates to methods and apparatus for controllably illuminating selected objects and areas of a scene in general, and in particular, to methods and apparatus for the adaptive and interactive lighting of such objects and areas.
2. Related Art
The term “structured lighting” has been applied to methods and apparatus for optical ranging, or triangulation, in which lines or other patterns of light are projected onto an object, reflected from it, and detected by a camera disposed at an angle relative to the projected light in such a way that certain three-dimensional information about the object, e.g., its shape, distance, size and location, can be determined from the reflected light. (See, e.g., U.S. Pat. No. 6,592,371 to D. Durbin et al.) Such structured lighting techniques have found wide application in certain “machine vision” applications, e.g., robotics, and in manufacturing, in which structured lighting has been used for precision alignment, positioning, and inspection purposes.
In a broader sense, the term structured lighting has also been used to refer to methods and apparatus for selectively illuminating or lighting objects in a field or a scene, such as in architectural lighting, e.g., in museums, and those used in photography and the film and theater arts, to achieve certain desirable lighting objectives, e.g., enhanced visibility, contrast, safety, and dramatic effects. While “adaptive” forms of such prior art structured lighting techniques are known, i.e., the controlled projection of light onto selected objects or portions of a scene based on feedback received from the scene, these tend to be relatively crude and imprecise techniques that require generally static scenes and frequent human intervention, and are not amenable to either the application of modern digital imaging techniques, or to being made “interactive” with objects in the illuminated scene, i.e., enabling the illuminated objects to cooperate, actively or passively, with the lighting system, to affect the projected illumination in a desired way.
For example, it is well known for photographers and film and stage set lighting engineers to measure the light incident upon or reflected from objects in a scene with a light meter, and to then adjust the number, position, color and intensity of a variety of light sources, reflectors and the like in accordance with the measurements taken to obtain the necessary exposure or desired scene lighting effects. It is even possible to “program” the lighting system in a limited sense to accommodate changes in the scene, providing sufficient time is taken between the changes to effect and check the lighting alterations. However, the procedures involved tend to be clumsy, time-consuming, and require the participation of highly skilled lighting technicians. It would therefore be desirable to provide a set lighting system that could, on a real-time basis, adaptively generate and project predetermined levels and colors of illumination onto all of the objects of a dynamic performance scene in accordance with the choreography of the performance.
Another well known example of adaptive lighting involves vehicular headlights. All road-legal vehicles are required to be equipped with headlights for use in the dark, as well as switches for “dimming” the headlights, which are actually used to deflect the beam of the vehicle's headlights downward, so that drivers of oncoming vehicles will not be dangerously blinded by the glare of the approaching headlights. This may be effected manually, with a foot- or hand-manipulated switch, or in some vehicles, automatically, by sensors that detect the headlights of the oncoming vehicle, and responsively, effect the dimming switching. However, such systems suffer from a common drawback, namely, that while the vehicle's headlights are dimmed, i.e., deflected downward, the driver's visibility of the road ahead is substantially impaired, particularly in low ambient lighting conditions. While adaptive headlight systems have been proposed that overcome this problem by “projecting” a dark spot on only the frontal area of the oncoming vehicle while brightly illuminating the surrounding area, such as that described in U.S. Pat. App. Pub. No. 2003/0137849 by R. M. Alden, these suffer from a second problem recognized as inherent in such adaptive headlight systems, viz., that if two approaching vehicles are equipped with such an adaptive system, the operation of both lighting systems becomes unstable, i.e., they both oscillate between bright and dim as the vehicles approach each other. It would therefore be desirable to provide an adaptive, interactive headlight system in which two opposing vehicles, each equipped with such a system, will each experience negligible headlight glare from the other, as well as a “high-beam” illumination of the road ahead.
A long-felt but as yet unsatisfied need therefore exists for an adaptive, interactive lighting system that enables the selective, controllable illumination of the objects and areas of a scene that is amenable to sophisticated digital image processing techniques, and that can be effected automatically and in real time.